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Matthews, Stephen John. "Cavitation erosion of aluminium alloys, aluminium alloy/ceramic composites and ceramics." Thesis, Coventry University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317927.
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Walker, John Christopher. "Lubricated sliding wear of some aluminium alloy composites." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434551.
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Turner, Travis Lee. "Thermomechanical Response of Shape Memory Alloy Hybrid Composites." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29771.
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This study examines the use of embedded shape memory alloy (SMA)actuators for adaptive control of the themomechanical response of composite structures. Control of static and dynamic responses are demonstrated including thermal buckling, thermal post-buckling, vibration, sonic fatigue, and acoustic transmission. A thermomechanical model is presented for analyzing such shape memory alloy hybrid composite (SMAHC) structures exposed to thermal and mechanical loads. Also presented are (1) fabrication procedures for SMAHC specimens, (2) characterization of the constituent materials for model quantification, (3) development of the test apparatus for conducting static and dynamic experiments on specimens with and without SMA, (4) discussion of the experimental results, and (5) validation of the analytical and numerical tools developed in the study.
The constitutive model developed to describe the mechanics of a SMAHC lamina captures the material nonlinearity with temperature of the SMA and matrix material if necessary. It is in a form that is amenable to commercial finite element (FE) code implementation. The model is valid for constrained, restrained, or free recovery configurations with appropriate measurements of fundamental engineering properties. This constitutive model is used along with classical lamination theory and the FE method to formulate the equations of motion for panel-type structures subjected to steady-state thermal and dynamic mechanical loads. Mechanical loads that are considered include acoustic pressure, inertial (base acceleration), and concentrated forces. Four solution types are developed from the governing equations including thermal buckling, thermal post-buckling, dynamic response, and acoustic transmission/radiation. These solution procedures are compared with closed-form and/or other known solutions to benchmark the numerical tools developed in this study.
Practical solutions for overcoming fabrication issues and obtaining repeatable specimens are demonstrated. Results from characterization of the SMA constituent are highlighted with regard to their impact on thermomechanical modeling. Results from static and dynamic tests on a SMAHC beam specimen are presented, which demonstrate the enormous control authority of the SMA actuators. Excellent agreement is achieved between the predicted and measured responses including thermal buckling, thermal post-buckling, and dynamic response due to inertial loading.
The validated model and thermomechanical analysis tools are used to demonstrate a variety of static and dynamic response behaviors associated with SMAHC structures. Topics of discussion include the fundamental mechanics of SMAHC structures, control of static (thermal buckling and post-buckling) and dynamic responses (vibration, sonic fatigue, and acoustic transmission), and SMAHC design considerations for these applications. The dynamic response performance of a SMAHC panel specimen is compared to conventional response abatement approaches. SMAHCs are shown to have significant advantages for vibration, sonic fatigue, and noise control.Ph. D.
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Coleman, Sarah L. "The corrosion of metal matrix composites." Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303434.
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Kang, Hyung-gu. "Locally reinforced squeeze cast aluminium alloy metal matrix composites." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294391.
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Jiang, Xia. "Development of Al alloy composites by powder metallurgy routes." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ee89b51e-386d-48c8-8f45-161e94490fb6.
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Particulate reinforced Al alloy composites (AlMCs) are recognized as important structural materials due to their lightweight, high modulus and strength and high wear resistance. In order to understand the effect of matrix, reinforcement and secondary processing techniques on the microstructure development and mechanical properties of AlMCs produced by powder metallurgy routes, Al alloy composites reinforced with three types of reinforcements by different secondary processing techniques have been produced and examined. Fabrication of Al or 6061Al alloy based composites reinforced with nano-sized SiC particles (~500nm), micro-sized (<25µm) quasicrystalline alloy particles (hereinafter referred to as “NQX”) and micro-sized Nb particles (~130µm) has been carried out by powder metallurgy routes followed by extrusion or cold rolling. After extrusion, a homogeneous distribution of secondary particles has been obtained with rare interfacial reaction products. The 6061Al/SiC composites exhibit superior mechanical properties than either monolithic alloys or composites reinforced with micro-sized particles with retained ductility while the 6061Al/NQX and 6061Al/Nb composites show limited improvement in tensile strength mainly due to their reinforcement size and poor interfacial bonding. After cold rolling, the evolution in microstructure, texture and strength has been analysed. A typical near β fibre texture with highest intensities near Copper and Brass orientations has been developed for 6061Al/NQX and 6061Al/Nb composites. For 6061Al/SiC composites, a randomized texture with very small grains has achieved due to the presence of the non-deformable SiC particles. Mechanical property tests including microhardness, three-point bending tests and tensile tests have been carried out on cold rolled samples and the results exhibit some level of improvement when compared with as-extruded samples due to work hardening. Finally, the work moves on to the general discussion based on the previous result chapters. The microstructural development related to reinforcement, matrix and interfacial areas during extrusion and cold rolling has been summarised and the correlation between microstructure and mechanical properties has been discussed. The thesis provides a thorough understanding of AlMCs produced by powder metallurgy routes in terms of matrix, reinforcement and processing techniques. It can provide reference to the future development of AlMCs for high strength applications.
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Bawane, Kaustubh Krishna. "Silicon Carbide - Nanostructured Ferritic Alloy Composites for Nuclear Applications." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96403.
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Silicon carbide and nanostructured ferritic alloy (SiC-NFA) composites have the potential to maintain the outstanding high temperature corrosion and irradiation resistance and enhance the mechanical integrity for nuclear cladding. However, the formation of detrimental silicide phases due to reaction between SiC and NFA remains a major challenge. By introducing a carbon interfacial barrier on NFA (C@NFA), SiC-C@NFA composites are investigated to reduce the reaction between SiC and NFA. In a similar way, the effect of chromium carbide (Cr3C2) interfacial barrier on SiC (Cr3C2@SiC) is also presented for Cr3C2@SiC-NFA composites. Both the coatings were successful in suppressing silicide formation. However, despite the presence of coatings, SiC was fully consumed during spark plasma sintering process. TEM and EBSD investigations revealed that spark plasma sintered SiC-C@NFA and Cr3C2@SiC-NFA formed varying amounts of different carbides such as (Fe,Cr)7C3, (Ti,W)C and graphite phases in their microstructure. Detailed microstructural examinations after long term thermal treatment at 1000oC on the microstructure of Cr3C2@SiC-NFA showed precipitation of new (Fe,Cr)7C3, (Ti,W)C carbides and also the growth of existing and new carbides. The results were successfully explained using ThermoCalc precipitation and coarsening simulations respectively.
The oxidation resistance of 5, 15 and 25 vol% SiC@NFA and Cr3C2@SiC-NFA composites at 500-1000oC temperature under air+45%water vapor containing atmosphere is investigated. Oxidation temperature effects on surface morphologies, scale characteristics, and cross-sectional microstructures were investigated and analyzed using XRD and SEM. SiC-C@NFA showed reduced weight gain but also showed considerable internal oxidation. Cr3C2@SiC-NFA composites showed a reduction in weight gain with the increasing volume fraction of Cr3C2@SiC (5, 15 and 25) without any indication of internal oxidation in the microstructure. 25 vol% SiC-C@NFA and 25 vol% Cr3C2@SiC-NFA showed over 90% and 97% increase in oxidation resistance (in terms of weight gain) as compared to NFA. The results were explained using the fundamental understanding of the oxidation process and ThermoCalc/DICTRA simulations.
Finally, the irradiation performance of SiC-C@NFA and Cr3C2@SiC-NFA composites was assessed in comparison with NFA using state-of-the-art TEM equipped with in-situ ion irradiation capability. Kr++ ions with 1 MeV energy was used for irradiation experiments. The effect of ion irradiation was recorded after particular dose levels (0-10 dpa) at 300oC and 450oC temperatures. NFA sample showed heavy dislocation damage at both 300oC and 450oC increasing gradually with dose levels (0-10 dpa). Cr3C2@SiC-NFA showed similar behavior as NFA at 300oC. However, at 450oC, Cr3C2@SiC-NFA showed remarkably low dislocation loop density and loop size as compared to NFA. At 300oC, microstructures of NFA and Cr3C2@SiC-NFA show predominantly 1/2<111> type dislocation loops. At 450oC, NFA showed predominantly <100> type loops, however, Cr3C2@SiC-NFA composite was still predominant in ½<111> loops. The possible reasons for this interesting behavior were discussed based on the large surface sink effects and enhanced interstitial-vacancy recombination at higher temperatures. The molecular dynamics simulations did not show considerable difference in formation energies of ½<111> and <100> loops for NFA and Cr3C2@SiC-NFA composites. The additional Si element in the SiC-NFA sample could have been an important factor in determining the dominant loop types. SiC-C@NFA composites showed heavy dislocation damage during irradiation at 300oC. At 450oC, SiC-C@NFA showed high dislocation damage in thicker regions. Thinner regions near the edge of TEM samples were largely free from dislocation loops. The precipitation and growth of new (Ti,W)C carbides were observed at 450oC with increasing irradiation dose. (Fe,Cr)7C3 precipitates were largely free from any dislocation damage. Some Kr bubbles were observed inside (Fe,Cr)7C3 precipitates and at the interface between α-ferrite matrix and carbides ((Fe,Cr)7C3, (Ti,W)C). The results were discussed using the fundamental understanding of irradiation and ThermoCalc simulations.Doctor of Philosophy
With the United Nations describing climate change as 'the most systematic threat to humankind', there is a serious need to control the world's carbon emissions. The ever increasing global energy needs can be fulfilled by the development of clean energy technologies. Nuclear power is an attractive option as it can produce low cost electricity on a large scale with greenhouse gas emissions per kilowatt-hour equivalent to wind, hydropower and solar. The problem with nuclear power is its vulnerability to potentially disastrous accidents. Traditionally, fuel claddings, rods which encase nuclear fuel (e.g. UO2), are made using zirconium based alloys. Under 'loss of coolant accident (LOCA) scenarios' zirconium reacts with high temperature steam to produce large amounts of hydrogen which can explode. The risks associated with accidents can be greatly reduced by the development of new accident tolerant materials. Nanostructured ferritic alloys (NFA) and silicon carbide (SiC) are long considered are leading candidates for replacing zirconium alloys for fuel cladding applications. In this dissertation, a novel composite of SiC and NFA was fabricated using spark plasma sintering (SPS) technology. Chromium carbide (Cr3C2) and carbon (C) coatings were employed on SiC and NFA powder particles respectively to act as reaction barrier between SiC and NFA. Microstructural evolution after spark plasma sintering was studied using advanced characterization tools such as scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) techniques. The results revealed that the Cr3C2 and C coatings successfully suppressed the formation of detrimental reaction products such as iron silicide. However, some reaction products such as (Fe,Cr)7C3 and (Ti,W)C carbides and graphite retained in the microstructure. This novel composite material was subjected to high temperature oxidation under a water vapor environment to study its performance under the simulated reactor environment. The degradation of the material due to high temperature irradiation was studied using state-of-the-art TEM equipped with in-situ ion irradiation capabilities. The results revealed excellent oxidation and irradiation resistance in SiC-NFA composites as compared to NFA. The results were discussed based on fundamental theories and thermodynamic simulations using ThermoCalc software. The findings of this dissertation imply a great potential for SiC-NFA based composites for future reactor material designs.
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Moon, Hee-Kyung. "Rheological behavior and microstructure of ceramic particulate/aluminum alloy composites." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13638.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.Vita.
Includes bibliographical references (leaves 221-229).
by Hee-Kyung Moon.
Ph.D.
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Zantout, B. "The production and evaluation of squeeze cast Al-alloy matrix-short ceramic fibre composites." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/22082.
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Research work on metal matrix-fibre composites has concentrated in the past on aligned fibre composites. The poor transverse strength of these composites is seen as a major hindrance to their practical use in the majority of engineering applications because stresses exist in more than one direction. Materials with isotropic properties are preferred and consequently reinforcement of composites in three dimensions will be necessary. With this objective, an investigation was conducted to assess the method of fabrication and properties of A1-a110y reinforced with short fibres (SiC and A1 203) randomly oriented in three dimensions. Two composite systems were examined: Al-4.S Cu alloy reinforced with SiC fibre; and Al-3.7S Mg alloy reinforced with A1 203 fibre. The general approach was to establish a satisfactory manufacturing method for the composites before evaluating their mechanical properties. The vortex technique was used to introduce the fibres into the molten alloy. Pre-treatment of the fibres, to induce wetting, and the use of a specially designed device for fibre separation and introduction to the molten A1-ai10ys was found to be necessary so that a uniform distribution of fibres oriented in three dimensions could be achieved. The composites were squeeze cast, under conditions which were experimentally determined, to ensure the production of pore-free castings with fine equiaxed structures. The improvement in tensile strength and ductility of the cast metal, provided by squeeze casting, would be beneficial to composite properties. Composite castings, with up to 10% volume fibre, were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and the respective molten alloy must be closely controlled so that fibre reinforcement can be realised. In this respect the optimum time of contact between the fibres and the molten alloy was experimentally defined for both composite systems. The tensile properties (UTS, 0.1% proof stress, and ductility) of the fibre-free alloys were substantially improved by squeeze casting. The addition of fibre produced further substantial improvement in the tensile properties of the squeeze cast composites, in particular elastic modulus and 0.1% proof stress. Furthermore, composite properties were isotropic. The improvement in the tensile properties of composite castings (as a result of the addition of fibre) was maintained at elevated temperatures. At 250oC, castings of both composite systems with 10% (volume) fibre had 0.1% proof stress and elastic modulus values similar to those for the fibre-free castings at room temperature. The tensile properties of the composite castings were not affected by thermal cycling (at experimental conditions). The fatigue life of the squeeze cast composite was substantially improved over and above the initial improvement in fatigue life of the fibre-free castings produced by squeeze casting. Wear of cutting tools was adversely affected by the presence of fibres.
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Oguocha, Ikechukwuka N. A. "Characterization of aluminum alloy 2618 and its composites containing alumina particles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/NQ37903.pdf.
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Regensburg, Anna. "Development of friction stir processing of CNT - reinforced aluminum alloy composites." Master's thesis, Pontificia Universidad Católica del Perú, 2012. http://tesis.pucp.edu.pe/repositorio/handle/123456789/6225.
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Owing their wide range of exceptional properties, for example thermal conductivity values of
more than 3000W/(mK) and strength in the range of 100 GPa, Carbon Nanotubes (CNTs) have
recently gained much attention as reinforcement for composite materials.
Considering the practical application in metal matrix composites (MMCs), tranferring those
favourable properties from nano to macro scale represents a main challenge. Methods of the
powder metallurgy route show promising results so far, but also lead to long process times and
damage of the tublar structure of the CNTs due to prolonged ball milling times.
At this point, the application of Friction Stir Processing (FSP) for fabricating CNT-reinforced
MMCs offers the possibility to reduce process times and realize the required reinforcement at
the relevant location of the component. The process uses a specially designed tool with a pin to
plasticize the base material by frictional heating and thus incorporate the reinforcing material
by stirring it into the workpiece.
Investigations, that have been carried out on this subject, generally consider the unifom
dispersion of the CNTs within the matrix as the key challenge of this process. So far, the
solution herefore is the application of multipass-FSP in order to distribute the CNTs uniformly
by processing the weld up to five times with alternating welding direction. This method
usually leads to damage or even destruction of the tubular structure of the CNTs. Regarding
all investigations on this subject, it can be noticed, that only conventional tool profiles like
cylindrical or threaded were used for the experiments, though other profiles like square
or more complex ones are considered to exhibit an increased mixing effect. Therefore the
objective of the thesis is to analyse the performance of four different tool geometries under
varying parameters and their influence on the CNT dispersion and general MMC composite
properties. Channels were cut into an Al 5086 plate, filled with CNT-powder and processed
by the different tools. The results were evaluated by metallographic analysis, hardness and
electrical resistance measurement and SEM analysis. Among the different geometries, the
triangular profile produced defect-free welds over the whole parameter set and distributed the
CNTs uniformly along a wide area close to the weld surface.Tesis
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Liu, Changqi. "The low cycle fatigue behavior of aluminum alloy based particulate composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056483090.
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Khan, Kirity Bhusan. "Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/182.
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Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3.
In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics.
The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles.
The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement.
Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy.
Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ).
Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix.
The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics.
From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application.
The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.
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Yoon, Tae-Ho. "Adhesion study of thermoplastic polymides with Ti-6Al-4V alloy and PEEK-graphite composites." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134525/.
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Yakoub, M. M. "Squeeze casting of zinc-aluminium (ZA) alloys and ZA-27/SiC composites." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/25378.
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Engineering applications of the recently developed zinc-aluminium casting alloys have been restricted due to certain inherent disadvantages such as segregation. However, segregation can be overcome by thorough mh:!ng of the melt and close temperature control or by rapid solidification of the melt, which can be achieved by squeeze casting. A more serious problem exists in service if components are subjected to a modest temperature increase to about 80°C, when there is a drastic loss of strength. It was therefore thought that the incorporation of ceramic fibres in the matrix could improve the properties of the material at modestly elevated temperatures. In the majority of engineering applications, stresses exist in more than one direction, so castings with isotropic properties are preferred and consequently reinforcement of composite in three dimensions would be necessary to maintain isotropic properties. An investigation was conducted to establish the influence of squeeze casting on the mechanical properties and structure of ZA-8, ZA-12 and ZA-27 alloys. The relationship between these factors and controlled process variables such as die temperature and applied squeeze pressure was established. The mechanical properties of the castings at room temperature and the effect of ageing at 95°C on tensile strength and dimensional changes were established. The results showed a substantial improvement in the tensile strength of the 'as-cast' squeeze cast alloys when compared with the 'as-cast' gravity die cast alloys. In the case of ZA-27 alloy, squeeze casting significantly improved ductility, which is a feature of benefit for all composite systems. The results also showed that pressure and die temperature substantially affect dimensional changes of the alloys when aged at 95°C. A major aspect of the research was the evaluation of the mechanical properties of the fibre reinforced ZA-27 alloy at elevated temperatures. Short silicon carbide fibres were randomly oriented in the matrix to obtain isotropic properties by a technique involving squeeze infiltration, followed by remelting and dispersal in the melt using specially designed equipments. Squeeze casting was used in the final stage of the composite fabrication. Castings of squeeze cast composite (with up to 10% volume fibre) and squeeze infiltrated composite (with up to 18-20% volume fibre) were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and molten alloy must be closely controlled for optimum properties of the composite. In this respect, the optimum time of contact between the fibre and the molten alloy was experimentally determined. It was found that the fibre supplied was of inferior tensile strength, which resulted in poor tensile strength of the tested composite up to a temperature of 100°C. However, the fibre brought substantial Improvement ln the tensile strength of the composite when tested at temperatures of 150 to 250°C. The modulus of elasticity of the composite was substantially improved at room temperature as well as at elevated temperature. The fatigue life of the squeeze cast composite was improved compared with squeeze cast matrix alloy (fibre-free). Squeeze cast composites with 3% volume fibre showed an Improvement in tribological properties compared with squeeze cast matrix alloy and squeeze cast and squeeze infiltrated composites with higher volume percentage of fibre. Wear of cutting tools was adversely affected by the presence of fibre.
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Mwita, Wambura Mwiryenyi. "Development and testing an intelligent hybrid polymeric composite beam with healing ability embedded with Ni-Ti shape memory alloy." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1251.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.Hybrid polymeric composites (HPC) are widely used for the design of aerospace, automobile and civil engineering structures. One of the major challenges posed by these materials and structures is their brittle nature. When subjected to impact and dynamic loads, the polymeric composite structures undergo micro cracking. The cracks coalesce, propagate and can lead to catastrophic failure of the material and structures. In this thesis, an intelligent hybrid polymeric composite (IHPC) beam with healing ability was developed and tested. The IHPC beam developed consisted of a 3% prestrained 1mm diameter Ni-Ti shape memory alloy (SMA) wire actuator embedded in the polymeric host matrix. The function of the embedded Ni-Ti shape memory alloy was to enhance intelligence and healing ability to the IHPC beam. Upon electric current resistance heating, the Ni-Ti SMA actuator responds by contracting as a result of detwinned martensite → austenite phase transformation. Contraction of the SMA in the IHPC beam was utilized to stiffen and enhance healing by retarding crack growth and recovery of the strain induced in the loaded IHPC beam. This can result to increase of the flexural stiffness EI (defined as the product of the Young’s Modulus E of the material and the moment of inertia I of the geometry of the beam) and mode I fracture stress intensity factor KIC of the IHPC beam. One (1) mm diameter Ni-Ti SMA wire was used in the experimental work in this thesis. The wire was cut into 35 pieces, 200 mm long each. Ni-Ti SMA wires were heated in the furnace to a temperature of 250ºC for ten (10) hours then were left to cool in the ambient air. The heat treatment was aimed to release any residual stress and to stabilize the austenite start (AS) and austenite finish (Af) transformation temperatures of the Ni-Ti SMA. After heat treatment, the Ni-Ti SMA wires were prestrained by 3% (based on a gauge length of 150mm) on a tensile testing machine. Prestraining of the Ni-Ti SMA wires was aimed to induce detwinned martensite volume fraction in them hence increasing the transformation strain and recovery force of the Ni-Ti SMA actuator. Intelligent hybrid polymeric composite (IHPC) beams and polymeric virgin (PV) beams, all of dimensions 150mmx25mmx10mm were manufactured by casting 60D polyurethane thermosetting epoxy resin in a silicon mould. transformation strain and recovery force of the Ni-Ti SMA actuator.
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Coelho, Reginaldo Teixeira. "The machinability of aluminium-based SiC reinforced metal matrix composite (MMC) alloy with emphasis on hole production." Thesis, University of Birmingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340966.
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Karnezis, Panos A. "Processing and mechanical properties of Al-alloy/SiC particulate metal matrix composites." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308616.
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Al-Jumaili, Omar Saad Salih. "Investigation of friction stir welding of aluminium alloy and aluminium matrix composites." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/55637/.
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Friction stir welding (FSW) is an upgraded version of the conventional friction welding process, and it is considered the latest development and the most important one during the past two decades in the welding of metals. The dependence of FSW on friction and plastic work as a heat source precludes the melting in the workpiece and leads to avoiding many of the difficulties arising from the change in the state of the material, such as defects, distortion and residual stresses, which often happen in conventional welding processes. FSW gained significant attention as a solid-state welding process of aluminium alloys, but now there is a need to extend its application to advanced materials such as metal matrix composites (MMCs). However, the process has always represented a challenge owing to the complexity of microstructural development and the associated number of process parameters to take into consideration. This thesis investigates the feasibility of welding two new advanced aluminium matrix composites (AMCs), AA 6092/SiC/17.5p-T6 and AA 6061B/SiC/20p-T1 by FSW for the first time. Also, aluminium alloy AA6082-T6 has been investigated as base-line material to specify the benefit, drawback, and FSW window. Experiment analyses were conducted to evaluate the influence of FSW parameters, including tool rotation and traverse speeds on the quality of weldments. Weld joints were characterised in terms of thermal history, metallurgical behaviour, mechanical properties, and residual stresses. The metallurgical characterisations have been done by optical, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Microhardness, tensile, and low-cycle fatigue (LCF) test with the axial total strain-amplitude control mode R=ε_min⁄(ε_max=-1) were used for evaluating the mechanical properties. The results showed that the generated peak temperature in the welding joints is affected more significantly by the rotating tool speed, while the exposure time and subsequent cooling rate are controlled by tool traverse speed. The microstructure of nugget zone (NZ) exhibits an elliptical shape with a substantial grain refinement resulted from continuous dynamic recrystallisation (CDR) process with an increase in the fraction of high angle grain boundaries (HAGBs). The evolved grain size was greatly influenced by weld pitch as the ratio between tool traverse speed to tool rotation speed, which is a key parameter to control the amount of heat input, exposure time and cooling rate. In addition, in the case of AMCs more homogeneous distribution of reinforcement particles (SiC) coupled with particle refinement were formed in the NZ. The cross-weld microhardness profile revealed a significant difference in microhardness among the base metals, heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and NZ in the case of AA 6082 and AMC (AA 6092/SiC/17.5p), as they depend on the strengthening precipitate. Meanwhile, the hardness profile of AMC (AA 6061B/SiC/20p) FSW joints showed that there is no difference in the measured hardness between the welding zone and base materials because the welded joints are exposed to thermal history similar to the initial heat treatment condition of the base metal, T1, cooled from an elevated temperature shaping process and naturally aged. The tensile strength of AA6082, and AMC (AA 6092/SiC/17.5p) cross-weld FSW specimens was found to be lower than their base metals with a joint efficiency (the ratio of the tensile strength of joint to the tensile strength of base metal) of about 71 and 75 %, respectively. While for SAMC (AA 6061B/SiC/20p) FSW joints it is reached 108 % of that of the base metal. The low-cycle fatigue results indicate that the fatigue life of the cross-weld joints varies with grain size in the NZ, and it is always lower than that of the base metal. A significant improvement in fatigue life is found to be related to the finer equiaxed grains dominated by HAGBs in the NZ, as well as, to less gradient in the grain size of the cross-weld. Residual stresses are significant concerns associated with the welding process, as it can combine with applied stresses, which may lead to the reduction of structural properties. The result of residual stress measurement by neutron diffraction techniques exhibited a typical ''M'' profile, which indicates that compressive and tensile residual stress existed in the base metal and welding zone, respectively. This has not only provided an improved understanding of residual stresses in FSW joints but also has contributed to the validation of 3D fully coupled thermo-mechanical finite element (FE) model, which has been developed based on Coupled Eulerian-Lagrangian (CEL) technique. The model is also used to predict the thermal history and material flow in the FSW of aluminium alloy AA6082. The numerical results showed a good agreement with the experimental results.
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Huchler, Bernd Arthur. "Pressure infiltration behaviour and properties of aluminium alloy - Oxide ceramic preform composites." Thesis, University of Birmingham, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514104.
Full textAbstract:
In the pressure infiltration processing of Metal Matrix Composites (MMCs), molten metal is injected into a porous preform. This research investigated ways to optimize the processing and properties of MMCs with Al alloy matrices. A ceramic volume fraction of 0.30 to 0.40 was used to keep a preponderant metallic behaviour and the reactivity of MgO, TiO2, Al2O3-SiO2 and Al2O3-TiO2 preforms was compared to pure Al2O3. Two stages were found during infiltration: first, flow initiation characterised by the dynamic wetting angle ?dyn and, second, the advancing flow in the preform capillaries. Reactions were detected in the MMC but did not significantly influence the ?dyn. Unsaturated fluid flow was evaluated for the subsequent infiltration stage and good agreement was found between a numerical model and experimental data. The MMCs had improved properties compared to the pure alloy. Elastic moduli up to 148 GPa, bending strengths up to 456 MPa as well as reduced wear rate were found. The wear performance of extended ceramic ligaments, found in MMCs with spherical metal ligaments, exceeded all other materials. The improved understanding of the infiltration of preforms and the resulting MMC properties obtained in this research should lead to the development of tailorable composite materials.
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Ivester, Robin H. C. (Robin Hansell Corbin) 1979. "Fabrication and characterization of Ni-Mn-Ga ferromagnetic shape-memory alloy composites." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8090.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.Includes bibliographical references (leaves 46-48).
Ferromagnetic shape-memory alloys (FSMAs) are a recently-developed class of active materials which show large extensional strains when a magnetic field is applied. Shear strains of 6% have been observed at room temperature in martensitic Ni-Mn-Ga single crystals. The strain effect in Ni-Mn-Ga FSMAs is a result of twin boundary motion in the martensite phase, and can be induced by either field or stress. Most Ni-Mn-Ga FSMA research so far has focused on actuation in single crystals. However, the mechanical loss inherent to twin boundary motion also makes this material attractive for energy absorption/vibration damping applications. This thesis describes the preliminary investigation of FSMA/polymer composites for eventual use in vibration damping, and should serve as a stepping stone toward further studies. The research moved through four stages: suction-casting polycrystalline Ni-Mn-Ga alloys with suitable target compositions, processing the polycrystalline material into powder, fabricating FSMA/polymer composites, and preliminary characterization of the stress-strain behavior of these composites. Suction casting produced three polycrystalline alloys which all showed significant variance from the target compositions as well as a high degree of compositional inhomogeneity. From the composition, structural analysis, and magnetic characterization, it was determined that Alloy 1 was martensite at room temperature, while Alloys 2 and 3 were austenitic. Alloy 3 showed a martensite transition temperature around 10° C. While only one of the three alloys shows a majority of martensite at room temperature, it is likely that the powders made from the polycrystalline material cover a wide range of compositions, so results concerning the structure of the powders reflect only the major phase present. The powders were mixed with urethane polymer at powder volume fractions of 10%, 20%, and 30%, followed by curing in a 4.2 kOe field to align the particles. Scanning electron microscopy and magnetic characterization confirmed the alignment of particles into chains within the polymer matrix. The dynamic stress-strain behavior of composites was characterized for low stresses at various frequencies. The static stress-strain behavior of the composites under compressive loading to stresses of 10 MPa was also characterized. In the FSMA/polymer composite samples, the first compressive loading test gave a stress/strain curve which is linear with one modulus up to a threshold stress. Beyond this threshold stress, the curve is linear but with a smaller modulus. Successive compressive stress-strain curves exhibited a linear stress/strain relationship with a modulus value between those of the two regions in the first test, with some hysteresis in the stress-strain response present between the first and second tests. A urethane sample and a urethane/20% volume fraction Al powder composite, by comparison, showed only linear stress-strain behavior with no significant changes between the first and second compressive loading tests. It is likely that the observed stress-strain behavior of the FSMA composites derives from stress-induced twin boundary motion in the martensite phase present.
by Robin H.C. Ivester.
S.B.
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Mani, Mahesh Kumar. "Development of Fe-50Co alloy and its composites by spark plasma sintering." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/60869/.
Full textAbstract:
Composite strengthening was attempted to improve the mechanical strength and toughness of the brittle near equiatomic Fe-Co alloy. The matrix alloy chosen for this research falls in the Fe-(30-50) Co group, which are known for their highest saturation induction (B-sat) and Curie temperature among the commercial soft magnetic alloys. The reinforcements, which exhibited a wide range of aspect ratios, included SiC particulates, SiC whiskers and carbon nanotubes (CNTs). In order to minimize the interfacial reaction between the reinforcements and the Fe-50Co alloy (matrix) and to realise higher compact density, spark plasma sintering (SPS) was selected for rapid compaction of materials. Reinforcements were coated using electroless deposition with Ni-P, copper and cobalt to modify the interfacial chemistry and thickness, and hence the final properties of the composites. A comprehensive study on the sintering variables found, within the range of examination and under constant heating and cooling rates, the optimum maximum temperature, soaking time and mechanical pressure of 900oC, 2-5 minutes and 80 MPa to rapidly consolidate the Fe- 50Co alloy to near-theoretical density. The volume fraction and size of the ordered regions in the monolithic alloy and hence the magnetic properties, were sensitive to the heating rate, cooling rate, temperature at which the mechanical pressure was applied and removed and post heat treatments. The influence of reinforcement coatings on the wetting characteristics, and in turn the properties, was compared using SiC particulate Fe-50Co composites. The introduction of bare and coarse (20 μm) SiC particulates negatively affected both magnetic and mechanical properties. Electroless Co coating of particulates improved both the flexural properties and magnetic characteristics such as permeability and coercivity by promoting the formation of narrower interfaces and better bonding. The addition of bare and coated whiskers in Fe-Co alloys enhanced densification and grain growth of the matrix. Copper coating over whiskers was found to be not helpful in realising uniform dispersion, whereas Co and Ni-P coating aided to achieve uniform dispersion of whiskers in the matrix. The amorphous Ni-P coating on whiskers was nanocrystallised during the rapid sintering process and resulted in a material with highly improved mechanical strength and ductility in comparison to the monolithic and other whisker reinforced composite materials. A novel attempt to prepare bulk Fe based alloy composites reinforced with CNTs was also undertaken. Both soft magnetic and mechanical property enhancements were observed in composites with lower vol% of CNTs (i.e. < 1.5%, in the range of examination up to 10%) due to the improvement of compact density by CNTs. An increase in the CNT vol% produced a negative effect on saturation induction and mechanical properties due to the agglomeration of CNTs and reduction in compact density. SPS helped to retain the structural integrity of CNTs during processing. Electroless Ni-P coating over the CNTs helped to reduce the structural damage of CNTs during processing and to improve the mechanical strength and ductility at a marginal cost of saturation induction, in comparison to the monolithic compacts and bare CNT reinforced composites. To date accurate temperature assessment of the compact in the SPS die has been difficult due to the remote position of the pyrometer within the body of the die. It has been found that the ferromagnetic Curie transition can be successfully employed to calibrate SPS pyrometer during processing.
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Löbel, Martin, Thomas Lindner, and Thomas Lampke. "Enhanced Wear Behaviour of Spark Plasma Sintered AlCoCrFeNiTi High-Entropy Alloy Composites." MDPI AG, 2018. https://monarch.qucosa.de/id/qucosa%3A32461.
Full textAbstract:
High hardness and good wear resistance have been revealed for the high-entropy alloy (HEA) system AlCoCrFeNiTi, confirming the potential for surface protection applications. Detailed studies to investigate the microstructure and phase formation have been carried out using different production routes. Powder metallurgical technologies allow for much higher flexibility in the customisation of materials compared to casting processes. Particularly, spark plasma sintering (SPS) enables the fast processing of the feedstock, the suppression of grain coarsening and the production of samples with a low porosity. Furthermore, solid lubricants can be incorporated for the improvement of wear resistance and the reduction of the coefficient of friction (COF). This study focuses on the production of AlCoCrFeNiTi composites comprising solid lubricants. Bulk materials with a MoS2 content of up to 15 wt % were produced. The wear resistance and COF were investigated in detail under sliding wear conditions in ball-on-disk tests at room temperature and elevated temperature. At least 10 wt % of MoS2 was required to improve the wear behaviour in both test conditions. Furthermore, the effects of the production route and the content of solid lubricant on microstructure formation and phase composition were investigated. Two major body-centred cubic (bcc) phases were detected in accordance with the feedstock. The formation of additional phases indicated the decomposition of MoS2.
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Hu, Zhihao. "Studies on Sintering Silicon Carbide-Nanostructured Ferritic Alloy Composites for Nuclear Applications." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/81763.
Full textAbstract:
Nanostructured ferritic alloy and silicon carbide composite materials (NFA-SiC) were sintered with spark plasma sintering (SPS) method and systematically investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as density and Vickers hardness tests. Pure NFA, pure SiC, and their composites NFA-SiC with different compositions (2.5 vol% NFA-97.5 vol% SiC, 5 vol% NFA-95 vol% SiC, 97.5 vol% NFA-2.5 vol% SiC, and 95 vol% NFA-5 vol% SiC) were successfully sintered through SPS.
In the high-NFA samples, pure NFA and NFA-SiC, minor gamma-Fe phase formation from the main alfa-Fe matrix occurred in pure NFA 950 degree C and 1000 degree C. The densities of the pure NFA and NFA-SiC composites increased with sintering temperature but decreased with SiC content. The Vickers hardness of the pure NFA and NFA-SiC composites was related to density and phase composition. In the high-SiC samples, NFA addition of 2.5 vol% can achieve full densification for the NFA-SiC samples at relative low temperatures. With the increase in sintering temperature, the Vickers hardness of the pure SiC and NFA-SiC composite samples were enhanced. However, the NFA-SiC composites had relative lower hardness than the pure SiC samples. A carbon layer was introduced in the NFA particles to prevent the reaction between NFA and SiC. Results indicated that the carbon layer was effective up to 1050 degree C sintering temperature. Green samples of gradient-structured NFA-SiC composites were successfully fabricated through slip casting of an NFA-SiC co-suspension.Master of Science
25
Chang, Hong. "Processing and characterisation of 3-3 Al alloy/Al2O3 interpenetrating composites (IPCs)." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/34720.
Full textAbstract:
Aluminium alloys, reinforced with ceramic particles or fibres, are desired materials in high performance applications due to their superior properties. Amongst aluminium matrix composites, interpenetrating composites, with both the matrix and reinforcement three dimensional throughout the microstructure, are more promising in providing truly multi-functional properties. However, due to the poor wetting between most metals and ceramics, pressure is normally needed in processing. In this research, a pressureless infiltration technique was adopted, which has the advantage of offering complex shape capability, no risk of damaging the ceramic skeleton and is potentially cost-effective and suitable for commercialization. The aims were to produce Al alloy/Al2O3 interpenetrating composites using the pressureless infiltration technique; to optimize the processing for full infiltration; to understand the infiltration mechanism and to characterise the composites in terms of both their microstructure and mechanical properties.
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Ellis, Roger L. "Ballistic Impact Resistance of Graphite Epoxy Composites With Shape Memory Alloy and Extended Chain Polyethylene Spectra Hybrid Components." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/36564.
Full textAbstract:
Graphite epoxy composites lack effective mechanisms for
absorbing local impact energy often resulting in penetration
and a structural strength reduction. The effect of adding
small amounts of two types of high strain hybrid
components on the impact resis tance of graphite epoxy
composites subjected to projectiles traveling at ballistic
velocities (greater than 900 ft/sec) has been studied. The
hybrid components tested include superelastic shape
memory alloy (SMA), a material having an unusually high
stra in to failure (15 - 20%), and a high performance
extended chain polyethylene (ECPE) known as Spectraâ ¢,
a polymer fiber traditionally used in soft and hard body
armor applications. A 1.2% volume fraction superelastic
SMA fiber layer was embedded on the specimens front,
middle, and backface to determine the best location for a
hybrid component in the graphite composite. From visual
observation and energy absorption values, it was c
oncluded that the backface is the most suitable location for
a high strain hybrid component. Unlike the front and middle
locations, the hybrid component is not restricted from
straining by surrounding graphite material. However, no
significant increases in energy absorption were found when
two perpendicular SMA layers and an SMA-aramid
weave configuration were tested on the backface. In all
cases, the embedded SMA fibers were pulled through the
graphite without straining to their full potential. It is believed
that this is due to high strain rate effects coupled with a
strain mismatch between the tough SMA and the brittle
epoxy resin. However, a significant increase in energy
absorption was found by adding ECPE layers to the
backface of the composite . With only a 12% increase in
total composite mass, a 99% increase in energy absorption
was observed.Master of Science
27
Moravčík, Igor. "Metal Matrix Composites Prepared by Powder Metallurgy Route." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-367507.
Full textAbstract:
Ve všeobecnosti, poznatky o design slitin, jejich výrobě a výběru legujúcich prvků sú omezené na slitiny s jedním základním prvkem. Tento fakt ale výrazně limituje možnosti a volnost výběru prvků pro dosáhnuti speciálních vlastností a mikrostruktur. V poslední dekádě se ukázalo, že materiálová věda a inženýrství nejsou ještě zdaleka prozkoumané v důsledku objevu nové třídy materiálů nazvané vysoko entropické slitiny (HEA high entropy alloys). Jejich objev upoutal pozornost vědecké komunity. Základní koncept pro jejich design je, že namísto jednoho, nebo dvou základních prvků obsahují minimálně 5 prvků v podobných atomových koncentracích. V posledních letech se objevila skupina materiálů odvozená od HEA, nazvaná slitiny so střednou entropii (MEA medium entropy alloys). Na rozdíl od HEA ale obsahují 3, nebo 4 prvky. Táto práce je věnovaná studiu přípravy a charakterizaci HEA, MEA a jejich kompozitů s pomocí metod práškové metalurgie. V této práci byli dohromady zkoumány tři kompozice: AlCoCrFeNiTi0.5, Co1.5Ni1.5CrFeTi0.5 a CoCrNi, kompozity s kovovou matricí (MMC metal matrix composites) vyztužené částicemi B4C s CoCrNi jako matricí. Hloubková mikrostrukturní a mechanická analýza těchto materiálů byla provedena pomoví metod rastrovací a transmisní elektronové mikroskopie spojené s tahovými a ohybovými zkouškami. V průběhu celé studie se objevovaly problémy s kontaminací kyslíkem, co se projevilo vznikem značného množství oxidů v připravených materiálech. U Slitiny AlCoCrFeNiTi0.5 byla naměřena tvrdost přesahující 800 HV. Její houževnatost ale byla velice omezena. V její mikrostruktuře byly identifikovány částice in-situ TiC v důsledku přítomnosti organického, anti-aglomeračního činidla (metanolu) v mlecí misce. Tato reakce může být použita v budoucnu k přípravě MMC se záměrnou disperzí TiC. Na druhé straně, slitina CoCrNi ukázala vysoké hodnoty tažnosti (26%) a meze pevnosti přes 1000 MPa. Mikrostruktura obsahovala majoritní FCC fázi s BCC precipitáty. Tahle slitina byla z důvodu vysoké tažnosti zvolena pro přípravu kompozitu s výztuží B4C. V průběhu slinování ale došlo k reakci mezi přítomným Cr a B4C, které výsledkem byl Cr5B3 borid. Tento kompozit mel pevnost v tahu 1400 MP a extrémne jemnozrnnou strukturu. Celková tažnost ale klesla na 1.9 %. Slitina AlCoCrFeNiTi0.5, která mela strukturu složenou jen z FCC tuhého roztoku dosáhla nejlepší kombinaci mechanických vlastností s pevností přesahující 1300 MPa a dostatečnou tažností 4%. Prášková metalurgie se ukázala jako vhodná metoda pro přípravu HEA a MEA slitin a jejich kompozitů, s dobrou kombinací pevnosti a tažnosti. Tato metoda dovoluje měnit mikrostrukturní parametry připravených materiálů jednoduchou úpravou parametrů procesu.
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Hicks, Kevin Paul. "A study of magnesium and magnesium alloy composites containing alumina and silicon carbide-based fibres." Thesis, University of Bath, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359089.
Full text
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Keles, Ozgur. "Production And Characterization Of Alumina Fiber Reinforced Squeeze Cast Aluminum Alloy Matrix Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609726/index.pdf.
Full textAbstract:
The aim of the present study was to investigate the effects of different levels of Saffil alumina fiber addition, magnesium content in aluminum alloy matrix and casting temperature on the mechanical behavior, microstructure and physical properties of short fiber reinforced aluminum matrix composites. The main alloying element silicon was kept constant at 10 wt%. Magnesium contents were selected as 0.3 wt% and 1 wt%. Saffil alumina fiber preforms varied from 10 to 30 vol%. The casting temperatures were fixed at 750 °C and 800 °
C. Micro porosity was present at the fiber-fiber interactions. Closed porosity of the composites increased when fiber vol% increased, however, variation in casting temperature and magnesium content in matrix did not have influence on porosity. Hardness of the composites was enhanced with increasing fiber vol%, magnesium content in matrix and decreasing casting temperature. Alignment of fibers within the composite had an influence on hardness
when fibers were aligned perpendicular to the surface, composites exhibited higher hardness. The highest hardness values obtained from surfaces parallel and vertical to fiber orientation were 155.6 Brinell hardness and 180.2 Brinell hardness for AlSi10Mg1 matrix 30 vol% alumina fiber reinforced composite cast at 800 °
C and at 750 °
C, respectively. 30 vol% Saffil alumina fiber reinforced AlSi10Mg0.3 matrix composite cast at 750 °
C showed the highest flexural strength which is 548 MPa. Critical fiber content was found as 20 vol% for all composites.
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Li, Q. F. "Studies in the solidification behaviour of aluminium alloy/alumina metal matrix composites (MMC's)." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260364.
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Thurber, Casey Ray. "Electrodeposited Metal Matrix Composites for Enhanced Corrosion Protection and Mechanical Properties." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849736/.
Full textAbstract:
In the oil and gas industry, high corrosion resistance and hardness are needed to extend the lifetime of the coatings due to exposure to high stress and salt environments. Electrodeposition has become a favorable technique in synthesizing coatings because of low cost, convenience, and the ability to work at low temperatures. Electrodeposition of metal matrix composites has become popular for enhanced corrosion resistance and hardness in the oil and gas industry because of the major problems that persist with corrosion. Two major alloys of copper-nickel, 90-10 and 70-30, were evaluated for microbial corrosion protection in marine environments on a stainless steel substrate. Copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth. Literature surveying the electrodeposition of Cu-Ni incorporated with nano- to micro- particles to produce metal matrix composites has been reviewed. Also, a novel flow cell design for the enhanced deposition of metal matrix composites was examined to obtain the optimal oriented structure of the layered silicates in the metal matrix. With the addition of montmorillonite into the Ni and Cu-Ni matrix, an increase in strength, adhesion, wear and fracture toughness of the coating occurs, which leads to an increase corrosion resistance and longevity of the coating. These coatings were evaluated for composition and corrosion using many different types of instrumental and electrochemical techniques. The overall corrosion resistance and mechanical properties were improved with the composite films in comparison to the pure metals, which proves to be advantageous for many economic sectors including the oil and gas industry.
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Kharmachi, Imen. "Elaboration électrochimique des revêtements composites Ni-Co sur l'acier au carbone et étude des propriétés physico-chimique et anticorrosives." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2072.
Full textAbstract:
Dans ce travail, l’élaboration des revêtements électrolytiques Ni-Co par régimes continu et pulsé, sur acier ordinaire à partir d’un électrolyte support à faible teneur en nickel,a permis d’améliorer les propriétés physico-chimiques et anti corrosives. Cela a également entraîné la diminution de la toxicité du bain d’électrodéposition. Un plan Doehlert a été exploité afin d’optimiser les différents paramètres d’électrodéposition. D’une part, l’ajout des additifs (hydroquinone, gélatine et des nano-particules TiO2) dans l’électrolyte a un effet remarquable sur les propriétés physiques et chimiques des électro-dépôts (morphologie,teneur en cobalt dans le revêtement et micro-dureté…). Les alliages composites et nano composites formés sont plus compacts, moins poreux et présentent une meilleure adhérence et une granulométrie plus fine que le revêtement de base Ni-Co sans ajout d’additifs. D’autre part, ces dépôts conduisent à une amélioration de la protection contre la corrosion et une bonne stabilité dans le milieu agressif 3% NaClIn this work, the elaboration of Ni-Co coatings by pulse and continuous electroplating oncarbon steel substrate from a supporting electrolyte with low nickel content can produce betterphysicochemical and anticorrosive properties as well as reduce the toxicity of the plating bath.A Doehlert plan was exploited to optimize the various plating parameters. On the one hand,the addition of additives (hydroquinone, gelatin and TiO2 nanoparticles) in the electrolyte hasa remarkable effect on the physical and chemical properties of the deposits (morphology,content of cobalt in the coating and micro hardness…). Composites and nanocompositesalloys are more compact, less porous with finer texture and good adhesion than the base Ni-Co coating without addition of additives. On the other hand, these deposits have a betterprotection against corrosion and a good stability in aggressive media 3% NaCl
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Dyos, Kim. "Microstructural development during heat treatment of PM 2124 Al alloy and 20 vol% SiC composite." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265300.
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Kiesling, Thomas C. "Impact failure modes of graphite epoxy composites with embedded superelastic nitinol." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-09162005-115046/.
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Miller, David N. "The sintering of a-alumina reinforced aluminium alloy matrix composites / y David N. Miller." [St. Lucia, Qld], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18280.pdf.
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Kwon, Jonghan. "Characterization of deformation mechanisms in pre-strained NiAl-Mo composites and α-Ti alloy." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343796987.
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Lenahan, Kristie M. "Thermoelastic control of adaptive composites for aerospace applications using embedded nitinol actuators." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/44955.
Full textAbstract:
Aerospace structures have stringent pointing and shape control requirements during long-term exposure to a hostile environment with no scheduled maintenance. This makes them excellent candidates for a smart structures approach as current passive techniques prove insufficient. This study investigates the feasibility of providing autonomous dimensional control to aerospace structures by embedding shape memory alloy elements inside composite structures. Increasing volume fractions of nitinol wire were embedded in cross-ply graphite/ epoxy composite panels. The potential of this approach was evaluated by measuring the change in longitudinal strain with increasing temperature and volume fraction. Reduction of thermal expansion is demonstrated and related to embedded volume fraction.
Classical lamination theory is used to formulate a two-dimensional model which
included the adaptive properties of the embedded nitinol. The model was used to predict
the increased modulus and reduction of thermal strain in the modified plates which was
verified by the experimental data.
Master of Science
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Lin, Zhan. "Platinum and Platinum Alloy-Carbon Nanofiber Composites for Use as Electrodes in Direct Methanol Fuel Cells." NCSU, 2010. http://www.lib.ncsu.edu/theses/available/etd-03312010-171722/.
Full textAbstract:
In response to the energy needs of modern society and emerging ecological concerns, the pursuit of novel, low-cost, and environmentally friendly energy conversion and storage systems has raised significant interest. Among various energy conversion and storage systems, fuel cells have become a primary research focus since they convert chemical energy directly into electrical energy with high efficiency and low pollutant emissions. For example, direct methanol fuel cells (DMFCs), which supply the electrical energy by converting methanol to energy, are an ideal fuel cell system for applications in electric vehicles and electronic portable devices due to their relatively quick start-up, rapid response to catalyst loading, and low operating temperature. However, the wide commercial use of DMFCs in advanced hybrid electric vehicles and electronic portable devices is hampered by their high cost, poor durability, and relatively low energy and power densities. In order to address these problems, their research focuses on the development of highly active electrode catalysts coupled with a suitable electrode structure for the oxidation of methanol at the anode and the reduction of oxygen at the cathode to attain high efficiency of DMFCs, and subsequently lowering the cost. In this dissertation, the fabrication of novel platinum and platinum alloy nanoparticle-loaded carbon nanofibers (CNFs) for use as electrodes in DMFCs is demonstrated through electrospinning, carbonization, and deposition. The resulting CNF-based electrodes possess the properties of high electroactive surface area, good catalytic abilities towards the oxidation of methanol and the reduction of oxygen, and great long-time stability. As a result, DMFCs using these CNFs-supported platinum and platinum alloy nanoparticles as electrodes offer many advantages, such as improved electrocatalytic abilities, long-term stability, easy fabrication, low cost, and environmental benignity. Therefore, this new technology opens up new opportunities to develop high-performance electrode materials in the future for high-performance DMFCs, which are one of the promising power sources for consumer devices and electric vehicles, and play a critical role in solving the worldwide critical energy issue.
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Khasawneh, Firas Abdallah. "Characterization of drillability of sandwich structure of carbon fiber reinforced epoxy composite over titanium alloy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5871.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 13, 2007). Vita. Includes bibliographical references.
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Giles, Adam R. "Deflection and shape change of smart composite laminates using shape memory alloy actuators." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7698.
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Shape memory materials have been known for many years to possess the unique ability of memorising their shape at some temperature. If these materials are pre-strained into the plastic range, they tend to recover their original un-strained shapes via phase transformation when subjected to heat stimulation. In recent years, this shape memory effect (SME) or strain recovery capability has been explored in aerospace structures for actuating the real-time movement of structural components. Among all the shape memory materials, the nickel-titanium based shape memory alloy (SMA) has by far received the most attention because of its high recovery capabilities. Since SMAs are usually drawn into the form of wires, they are particularly suitable for being integrated into fibre-reinforced composite structures. These integrated composite structures with SMA wires are thus called smart adaptive structures. To achieve the SME, these wires are normally embedded in the host composite structures. In returning to their unstrained shape upon heat application, they tend to exert internal stresses on the host composite structures in which they are embedded. This action could result in a controlled change in shape of the structural components. Although there has been a significant amount of research dedicated to characterising and modelling the SME of SMA wires, little experimental work had been done to offer an in-depth understanding of the mechanical behaviour of these smart adaptive polymeric composite structures. This project examined the deflection and shape change of carbon/epoxy and glass/epoxy cantilever beams through heating and cooling of internal nitinol SMA wires/strips. The heat damage mechanism and cyclic behaviour are major factors in the operation of such a system and need to be clearly understood in order to develop and gain confidence for the possible implementation of future smart actuating systems. Therefore, the objectives of the proposed research were to investigate (i) effect of embedding SMA, wires on mechanical properties of host composite, (ii) assessment of single-cycle and multiple-cycle actuation performance of smart beams, and (iii) thermal effects of excessive heat on the surrounding composite matrix.
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Rey, Thierry. "Contribution to the elaboration, experimentation and modeling of architectured shape memory alloy Nickel-Titanium/silicone rubber composites." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI105.
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Les alliages à mémoire de forme Nickel-Titane sont connus pour leurs propriétés de superélasticité associées à une transformation martensitique élastique, de ferroélasticité liées à la réorientation de variantes de martensite et enfin de mémoire de forme. Les propriétés des matériaux architecturés NiTi, tels que des tricots, des matériaux cellulaires,… dépendent de celles de l'alliage NiTi constituant et de la structure géométrique. L'étude porte sur des matériaux architecturés composites constitués par des matériaux architecturés NiTi saturés par des élastomères silicones. De tels matériaux possèdent potentiellement une gamme étendue de propriétés dépendant à la fois des matériaux constitutifs, mais également des interfaces et de la topologie.La première partie du travail porte sur l'étude de l'interface NiTi silicone. Parmi les solutions testées, le traitement de surface par plasma a été particulièrement étudié. L'influence des paramètres du traitement plasma sur la qualité des interfaces a tout d'abord été étudiée grâce à des essais de pull-out réalisés sur des fils de NiTi enrobés dans des silicones. Les paramètres optimaux de traitement par plasma ont ensuite été appliqués pour élaborer des matériaux architecturés tubulaires constitués d'un tricot NiTi enrobé d'élastomère. Le comportement mécanique du composite ainsi obtenu a été caractérisé par des essais de traction et de gonflement.La deuxième partie de l'étude porte sur le comportement de l'élastomère silicone. Une campagne expérimentale a été menée afin de déterminer l'influence de la température sur le comportement mécanique du silicone, en particulier sur l'accommodation du matériau après la première charge (effet Mullins), l'hystérésis mécanique et la relaxation. Une loi de comportement prenant en compte l'hystérésis mécanique a ensuite été proposée. Inspirée par de nombreux travaux en mécanique des élastomères, l'approche utilise une décomposition de l'espace en un nombre fini de directions. Une loi monodimensionnel incluant les effets d'hystérésis est écrite pour chacune des directions. Ce modèle a été implémenté dans un code de calculs par éléments finis (Abaqus) et a été testé avec des calculs de structures.Dans la troisième partie de l'étude, le formalisme précédent a été utilisé afin de proposer un modèle pour le comportement mécanique du NiTi, en se restreignant dans cette première contribution à la superélasticité. La confrontation des résultats de simulation avec ceux de tests expérimentaux de la littérature sur des plaques isotropes et anisotropes montre les perspectives prometteuses d'une telle approcheShape memory alloys Nickel-Titanium are well known for their superelastic properties associated with a martensitic elastic transformation, ferroelasticity due to the reorientation of martensite and finally shape memory effects. The properties of architectured NiTi materials, such a knitted NiTi, cellular materials,… depend on the constituting NiTi and of the geometry. The study deals with architectured composite materials made of architectured NiTi materials and silicone rubber elastomer. Such materials present numerous different properties, depending on the constituting materials and also on the interfaces and the topology.The first part of the study focuses on the interface between NiTi and silicone rubber. Among the tested solutions, plasma treatments were especially studied. The influence of treatment parameters on the interface resistance was firstly investigated by means of pull-out tests carried out on NiTi wires embedded in a silicone rubber matrix. Optimized parameters for plasma treatment were then applied in order to elaborate a tubular architectured material made of knitted NiTi and silicone rubber. The mechanical behavior of this composite was characterized by means of tensile and swelling tests.The second part of the study deals with silicone rubber behavior. Experiments were performed in order to evaluate the influence of temperature on the mechanical behavior of silicone rubbers, especially on the stress softening (Mullins Effect), mechanical hysteresis and stress relaxation. A model taking into account the mechanical hysteresis was then proposed. Based on numerous works in the field of rubber mechanics, the approach used a decomposition of the space in a finite number of directions. A monodimensional constitutive equation including hysteresis effects is written for each direction. This model was implemented in a finite elements software (ABAQUS) and was tested with structure simulations. In the third part of the study, the previous formalism was used model the mechanical behavior of NiTi, only In case of superelasticity. The results of the simulations carried out are in good agreement with those reported in the literature for tests on isotropic and anisotropic NiTi plates, which highlights the great interest of such an approach
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Saal, Sheldon C. "The development of an active surface using shape memory alloys." Thesis, Cape Peninsula University of Technology, 2006. http://hdl.handle.net/20.500.11838/1292.
Full textAbstract:
This thesis work was conducted in the Department of Mechanical Engineering
at the Cape Peninsula University of Technology (CPUT) and was submitted
towards the partial fulfilment of the Masters Degree in Technology:
Mechanical Engineering.Recent years have witnessed a tremendous growth and significant advances in “smart” composites and “smart” composite structures. These smart composites integrate active elements such as sensors and actuators into a host structure to create improved or new functionalities through a clever choice of the active elements and/or a proper design of the structure. Such composites are able to sense a change in the environment and make a useful response by using an external feedback control system. Depending on their applications, smart composites usually make use of either the joint properties of the structure or the properties of the individual elements within the composites. The accumulation in the understanding of materials science and the rapid developments in computational capabilities have provided an even wider framework for the implementation of multi-functionality in composites and make “smart” composites “intelligent”.
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Terzak, John Charles. "Modeling of Microvascular Shape Memory Composites." Youngstown State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1389719238.
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Alobaid, Baleegh. "SYNTHESIS AND CHARACTERIZATION OF MAGNESIUM - TITANIUM COMPOSITES BY SEVERE PLASTIC DEFORMATION." UKnowledge, 2018. https://uknowledge.uky.edu/cme_etds/91.
Full textAbstract:
Magnesium alloys are widely used in engineering applications, including aerospace and automobile industries, due to their desirable properties, such as lower density, high damping capacity, relatively high thermal conductivity, good machinability, and recyclability. Researchers have, therefore, been developing new magnesium materials. However, mechanical and corrosion properties are still limiting many commercial applications of magnesium alloys. In this Ph.D. thesis research, I developed Mg-Ti composite materials to offer some solutions to further improve the mechanical behavior of magnesium, such as titanium-magnesium (Ti-Mg) claddings, Mg-Ti multilayers, and Ti particle enforced Mg alloys. Low cost manufacturing processes, such as hot roll-bonding (RB) and accumulative roll-bonding (ARB) techniques, were used to produce Mg-Ti composites and sheets. The microstructural evolution and mechanical properties of composites were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), nanoindentation, and tensile tests.
In the first part of this study, I investigated the bonding strength of the AZ31/Ti to understand the mechanical properties of Mg/Ti composites. Using a single pass RB process, I fabricated AZ31/Ti multilayers with the thickness reduction in a range of 25% to 55%. The hot-rolled AZ31/Ti multilayers were heat-treated at 400 °C for 6, 12, and 24 hours, respectively, in an argon atmosphere. Tensile-shear tests were designed to measure the bonding strength between AZ31/Ti multilayers. Furthermore, the experimental results revealed good bonding of the AZ31/Ti multilayers without forming any intermetallic compounds in the as-rolled and heat-treated AZ31/Ti multilayers. The good bonding between Ti and AZ31 is the result of diffusion bonding whose thickness increases with increasing heat-treatment time and thickness reduction. The shear strength of the Ti/AZ31 multilayer increases with increasing bonding layer thickness.
In the second part of this study, I characterized the microstructure and texture of three-layered Ti/AZ31/Ti clad sheets which were produced by single-pass hot rolling with a reduction of thickness 38% (sheet I) and 50% (sheet II). The AZ31 layer in sheets I and II exhibited shear bands and tensile twins {1012}⟨1001⟩ . The shear bands acted as local strain concentration areas which led to failure of the clad sheets with limited elongation. Heat treatment caused changes in the microstructure and mechanical properties of clad sheets due to static recrystallization (SRX) on twins and shear bands in the AZ31 layer. Recrystallized grains usually randomize the texture which causes weaken the strong deformed (0001) basal texture. Twins served as nucleation sites for grain growth during SRX. Tensile tests at room temperature showed significantly improved ductility of the clad sheets after heat treatment at 400°C for 12h. The results showed that the mechanical properties of clad sheets II are better than clad sheet I: The clad sheet II shows elongation 13% and 35% along the rolling direction (RD) for as-rolled and annealed clad sheet, respectively whereas the clad sheet I shows elongation 10% and 22% along RD for as-rolled and annealed clad sheet, respectively.
In the final part of this study, I examined the effects of dispersed pure titanium particles (150 mesh) with 0, 2.3, 3.5, 4.9, and 8.6 wt. % on the microstructure and mechanical properties of AZ31-Mg alloy matrix. Mg-Ti composites were processed through three accumulative roll bonding (ARB) steps using thickness reductions of 50% in each pass followed by heat treatment at 400 °C for 12 h in an argon atmosphere. ARB is an efficient process to fabricate Mg-Ti composites. Mechanical properties of Mg- 0Ti and Mg-2.3Ti composite were enhanced by ~ 8% and 13 % in yield strength and ~ 30% and 32 % in ultimate tensile strength, respectively. Meanwhile, the elongation of the composites were decreased by 63% and 70%, respectively. After heat treatment, the results showed a decrease in yield strength and increase in elongation to fracture. The mechanical properties of the Mg-0 and Mg-2.3Ti composite were enhanced: ultimate tensile strength by 9% and 7%, and elongation by 40% and 67%, while the yield strength was decreased by 28% and 36% compared with the initial AZ31. Enhancements of strength and ductility were the results of two mechanisms: a random matrix texture by ARB and ductile titanium particle dispersion.
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Subbarayan, Sapthagireesh. "Fabrication of a Novel Al/Mg Composite: : Processing and Characterization of Pure Aluminium, Al/AZ31 Alloy Bi-Metal and Aluminium based Sheet Composites by Severe Plastic Deformation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23778.
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Napolitano, Ralph E. Jr. "Finite differenc-cellular automation modeling of the evolution of interface morphology during alloy solidification under geometrical constraint : application to metal matrix composite solidification." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/32810.
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Yurcho, Anthony M. "Microstructural Investigation of Al/Al-Fe alloy-Al2O3 Interpenetrating Phase Composites Produced by Reactive Metal Penetration." Youngstown State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1315924042.
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Dan, Chengyi. "Effects of nanoparticles on the microstructure and crystallographic texture evolution of two Aluminium-based alloys." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS147.
Full textAbstract:
Les effets des nanoparticules (cisaillables et non-cisaillables) sur l’évolution microstructurale et l'évolution de la texture cristallographique des deux alliages à base d’aluminium après laminage à froid ont été étudiés dans cette thèse. Un alliage Al-Sc contenant des nanoparticules cisaillables de Al3Sc et un composite Al-TiB2 contenant des nanoparticules non-cisaillables TiB2 sont étudiés. La microscopie électronique en transmission (MET), la diffraction d'électrons rétrodiffusés (EBSD) et l’analyse de la texture par la diffraction de neutrons sont utilisées pour caractériser le développement de la microstructure et la texture cristallographique lors du laminage à froid des 2 alliages.La restauration dynamique pendant laminage a été inhibée dans la matrice contenant des Al3Sc nanoparticules cisaillables et TiB2 non-cisaillables. Par conséquent, peu de cellules de dislocation ont été générées dans la matrice, ce qui limite la diminution de la taille des grains.Le développement de la texture de laminage est retardé par les nanoparticules cisaillables ou les particules non-cisaillables. Des bandes d’orientation de cube résiduelles se trouvent dans les matériaux contenant des particules cisaillables dans une matrice très déformée en raison de la limitation du glissement croisé. La réduction de la proption volumique des composantes de texture du laminage se produit dans les matériaux contenant de grandes particules non-cisaillables (de l’ordre d’un micromètre) en raison de la recristallisation dans les PDZs (Particle Deformation Zones), ce qui contribue également à la diminution des grains.De plus, le cisaillement de nanoparticules favorise le glissades en plan, ce qui conduit à une forte localisation des déformations et à l'apparition de bandes de cisaillement. La génération de bandes de cisaillement dépend de l'orientation et est dû au changement soudain des chemins de déformation et et de l'inhibition de la récupération dynamique. Les nanoparticules non cisaillables ont probablement pivoté avec la matrice environnante, ce qui pourrait constituer un nouveau mécanisme de déformationThe effects of shearable and non-shearable nanoparticles on the microstructure and crystallographic texture evolution of two Al-based alloys after cold rolling have been studied in this thesis. An Al-Sc alloy containing shearable Al3Sc nanoprecipitates and Al-TiB2 composite containing non-shearable TiB2 nanoparticles are investigated, respectively. Transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and neutron diffraction texture analysis are employed to characterize the microstructure and texture development of the two alloys during cold rolling.Dynamic recovery has been inhibited in the matrix containing both shearable (Al3Sc) and non-shearable (TiB2) nanoparticles due to the pinning effects. Hence, few dislocation cells are generated in these matrices that impedes the grain refinement.The development of rolling texture is retarded by either shearable nanoprecipitates or non-shearbale particles. Obvious residual Cube orientation bands are found in materials containing shearable precipitates at the deformed states due to the limitation of cross-slip. Volume reduction of rolling texture components occurs in materials containing large non-shearable particles (about 1 micrometer) due to the recrystallization at PDZs (Particle Deformation Zones), which contributes to grain refinement.In addition, the shearing of nanoprecipitates promotes planar slip leading to strong strain localization and the occurrence of shearbands. The generation of shearbands is orientation dependent and results from the sudden change of deformation paths and inhibition of dynamic recovery. The non-shearable nanoparticles probably have rotated together with the surrounding matrix, which could be a new deformation mechanism
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Hahnlen, Ryan M. "Development and Characterization of NiTi Joining Methods and Metal Matrix Composite Transducers with Embedded NiTi by Ultrasonic Consolidation." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243886351.
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Kumar, Pawan. "Studies of wire-matrix interaction in some tungsten wire reinforced stainless steels." Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8980.
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There is potential for improving creep properties of stainless steels by reinforcing them with tungsten (W) wires. Past studies have shown that a detrimental factor that impairs the mechanical properties of tungsten wire reinforced superalloy composites is the formation of brittle intermetallic phases due to the interaction between W wire and constituents of the alloy matrices. Formation and growth of the intermetallic phases strongly depends on the matrix chemistry and for the retention of creep strength, matrix compositions that do not form intermetallic phases with tungsten are desirable for fabricating W wire reinforced composites for high temperature applications.
This research investigated the formation and growth of reaction phases in W wire reinforced 316L (W/316L) stainless steel and HP alloy steel (W/HP) that were fabricated by casting method. Additionally, the effect of composition on the evolution and kinetics of reaction phases was studied in some W wire reinforced experimental alloys based on Fe-Ni-Cr only (W/Fe-Ni-Cr). The fabricated composites were diffusion annealed in the temperature range 1000-1200°C for 25-500 hours. Microstructure and chemistry of the reaction phases in the as-cast and diffusion annealed composites were studied using scanning electron microscopy, energy dispersive spectroscopy and electron backscattered diffraction techniques. Growth kinetics of the reaction layers and average effective interdiffusion coefficients in the layers were determined for the composites.
Results showed that an intermetallic phase isostructural with µ-phase formed in the as-cast W/316L and W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratios. In W/HP a phase M12C with crystal structure similar to η-carbide was formed. These phases developed and formed brittle reaction layers around the W wires during diffusion annealing. A parabolic relationship between the µ-phase and η-carbide growth and diffusion annealing time indicated that the growth of reaction layers was diffusion controlled. In the W/Fe-Ni-Cr composites, formation of intermetallic phases did not occur in the matrices with 0.5Fe:Ni ratio, instead some isolated tungsten particles were observed in the matrix adjacent to the wires after diffusion annealing. In W/Fe-Ni-Cr composites with 1 and 2 Fe:Ni matrix ratio, the growth of µ-phase reaction layers during annealing was observed to be dependent on the matrix composition. It was found that with an increase in the Ni content in the matrix, growth of µ-phase reaction layer decreased.
The study presented in this thesis gives first-hand information on phase formation and growth kinetics of the reaction layers in W/316L and W/HP composites. It revealed that the interaction of W with 316L and HP alloy matrices leads to formation of cracked intermetallic and carbide reaction layers which are not desirable in the composites designed for high temperature applications. It has also been shown in this study that in W/Fe-Ni-Cr composites, intermetallic phase formation can be suppressed by increasing Ni content in the matrix. In the composite with high Ni contents in the matrix (0.5Fe:Ni ratio) intermetallic phases do not form even after diffusion annealing at 1200°C. This intermetallic free W/Fe-Ni-Cr composite can further be studied for its creep strength.